This invention relates to transfer mechanisms and, more particularly, this invention relates to a transfer mechanism for transporting containers and an improved conveyor drive unit therefor.
Generally, the instant invention relates to the automatic and sequential starting and stopping of a plurality of drive units relative to a predetermined parameter of the flow of articles along the transfer mechanism.
The transfer or conveyance of articles from one location to another during processing is universally used in industry. Various types of conveyor systems have been used including the use of chains having individual links hingedly connected together. When it is desired to transfer moving articles from one conveyor to another, the conveyors are often disposed at least partially alongside each other. A problem often occurs in this type of conveyor system which inherently uses a "dead plate" between conveyor stations in that the articles tend to remain on the dead plate if no articles immediately follow the moving articles to push them along. Also, there is nothing to prevent unstable articles from falling over when pushed onto or off of the dead plate. Moreover, the friction inherent between the chain and certain types of the moving articles which it supports could tend to cause backing up of the articles. This problem has been recognized and a solution has been provided with the use of rollers as means for supporting and conveying the articles.
With the use of rollers, there is much less contact area between the conveyor surface and the articles, thereby improving the control of the articles being transported. Moreover, as will be discussed below with reference to U.S. Pat. No. 4,313,536, separate drive systems can be implemented at various portions of a roller type conveyor system which further increases flexibility in the movement of the articles.
Various types of direct drives using a brake system have been devised, as in U.S. Pat. No. 3,621,982 issued to Fred J. Fleischauer on Nov. 23, 1971. In U.S. Pat. No. 3,621,982, a flexible band is disposed against certain powered conveyor rollers so that when tension is placed on the band, selected rollers are prevented from operating. Similarly, U.S. Pat. Nos. 3,650,375, 3,696,912 and 3,961,700, issued on Mar. 21, 1972, Oct. 10, 1972 and June 8, 1976, respectively, to Fred J. Fleischauer et al., teach roller brakes wherein each roller is connected to a pulley by a resilient drive belt. However, the braking devices in the above-described Fleischauer patents are inefficient in that the drive belt can wear out and the tension derived therefrom decreases after a prolonged operation.
Another conveyor driving device has been described in U.S. Pat. No. 3,631,964 issued to Ronald C. Hinman on Jan. 4, 1972. In the Hinman apparatus, a propulsion roller is provided adjacent to an operating roller as a supplement. The propulsion roller in Hinman has on its end portion a clutch actuator which can drive the roller in a desired direction, but requires manual operation thereof (see, also, U.S. Pat. No. 3,610,406 issued to Fred J. Fleischauer on Oct. 5, 1971). In U.S. Pat. No. 3,327,837 issued to G.P. Covell on June 27, 1967, a fluid-operated clutch is used with an idle or gravity roll of a roll-type conveyor. In U.S. Pat. No. 3,667,589 issued to Charles F. Constable on June 6, 1972, a deactivating drive apparatus is disclosed with a longitudinal shaft which can be individually connected to a drive roll. The Covell and Constable patents however lack the flexibility of activating a desired set of drive rollers.
In addition to the above-mentioned deficiencies of the above-described devices, there was no solution to the problem of the continued running of one or more elements of the transfer system thereby possibly resulting in damage to the articles. During the accumulation of articles being transported, the pathways of the transfer system may be blocked off and the operation of the system must be either stopped or curtailed. Although U.S. Pat. No. 3,782,515, issued to W.E. Cowen, Jr. on Jan. 1, 1974, attempts to resolve the problem by providing for automatic halting of a conveyor during accumulation, the Cowen apparatus however uses a drag-responsive torsion spring which responds to a clutch when a pin is depressed under a shaft load in excess of a critical value. The activating mechanism in Cowen is not however directly controlled by the articles being transported thereby increasing the chance of halting a specific roller when not desired. Moreover, Cowen uses a spring activating device which is cumbersome to maintain or repair. Further, due to an indirect control by the articles, relieving of pressure due to article accumulation is inefficient.
U.S. Pat. No. 4,313,536 issued on Feb. 2, 1982 to Frederick E. Fauth, Sr. provides significant improvements over the use of chains. Moreover, U.S. Pat. No. 4,313,536 provides a significant feature of providing separate drive systems in order to obtain flexibility in the movement of articles. The present invention is a device for significantly improving a conveyor system like U.S. Pat. No. 4,313,536 which is embodied herein in its entirety by reference. It is in this separate drive unit, as in U.S. Pat. No. 4,313,536, which when added to a roller-type conveyor system contributes to the significant advantage of being able to automatically control various portions of the conveyor system. But, the system of U.S. Pat. No. 4,313,536 does not provide for "zero pressure" accumulation. By "zero pressure" accumulation is meant accumulation of articles without any significant pressure being applied thereto by the mass of articles being accumulated.
Accordingly, there is a need for an efficient, economical, simply constructed and easily installed means and method of operation thereof for providing a true "zero pressure" (i.e., a smooth transport of articles) during operation of an article transfer system by automatically, directly, individually and sequentially controlling the system by the articles themselves. The drive unit used in the present invention satisfies such a need. The drive unit of the instant invention embodies a simply constucted combination of inexpensive, easily accessible and rapidly manufactured parts, yet efficient when used in an article transfer system in providing a true "zero pressure" (i.e., absence of pressure applied by the articles to abutting articles during accumulation).